When I try to install json gem (gem install json), at first it fails to do so, because of some dev package issue. After fixing it, it fails saying that "sh: make: command not found" and "ERROR: Error installing json: ERROR: Failed to build gem native extension.". Why is it failing on make? Notice this is not Mac, this is in RHEL 5 (4 or 5, not sure). Why is it not able to do some "build gem native extension"?